Production of resinous felted fibrous composition



' the extraction of such as asphalts Patented Oct. 23,, 1945 PRODUCTIONOF acsnvous FELTED Finao s COMPOSITION Herman W. Richter, Bridgewater,and Harold R.

Gillette, Newton Highland Federal Electric Company, a corporation of NewYork s, Mass, assignors to Inc., Chicago, Il

lilo Drawing. Original application August 29, i

1940, Serial No.

354,628. Divided and this application November 17, 1941, Serial No.419,430

2 Claims. This invention relates to the production of resinous feltedfibrous compositions from a combination of fibrous pulp and a resinderived from pine wood pitch, which composition is susceptible toconsolidation under heat and pressure to produce a homogeneous producthaving physical properties particularly suitable for structural uses andother purposes.

This application is a division. of our co-pending application Serial No.354,628 filed August 29, 1940, now Patent No. 2,264,189.

The felted fibrous material of our invention is capable of beingconsolidated to produce products having a relatively wide range ofthickness, of the order of one-eighth inch to one inch, more or less, byuniting a plurality of thin component layers to form a truly homogeneousstructure capable of being machined, handled and used,

distinguished in character and properties from the component materialsor intermediate products, although in its broader aspects our inventioncontemplates the production of such a homogeneous product byconsolidating a thick single layer of our composition.

' The intermediate and final products of our invention are of thethermoplastic rather than the thermo-setting or thermo-curing type. Theconsolidated product is highly resistant to water and moisture andresistant to petroleum solvents in general; is highly non-brittle eventhough the resin is per se extremely frangible and brittle. Othercharacteristics and properties of the final consolidated product will bebrought out later in this specification.

Felted fibrous compositions utilizing synthetic and natural resins,treated or modified, or untreated or unmodified, have been proposed.However, the employment of such resins involves a cost factor which isof commercial significance, and other well recognized shortcomings.

In our invention there is employed, in conjunction with the fibrouspulp, a plastic resinous material which is inexpensive and available inlarge quantities and which, when properly combined with the fibers andconsolidated in accordance with our invention results in a product ofrelatively considerable resistance to the absorption of moisture and towarping, and which, together with a pleasing appearance, has desirablestructural properties particularly in respect to rigidity and resistanceto cracking, shattering, breakage or separation.

Felted fibrous products made with bitumens,

and coal tar pitches, or with resins, such as cumar, are characterizedby inferior resistance to deformation under moderately elevatedtemperatures, by surface instability, by inferior resistance tohydrocarbon oils, and in some instances by inferior resistance to waterand moisture; and such products do not have satisfactory propertiesafter being composited or consolidated under heat and pressure.

Our consolidated product possesses a desirable range of elasticresistance to deformation winch renders it durable in normal use; hasdesirable resistance to deiormation under moderately elevatedtemperatures such as would be encountered in many uses, and hasexceptionally desir able surface'stability.

The invention more particularly comprehends a series of related stepsil'l'WhlCh the resinous material is incorporated by suitable beatertreat-, ment with fibrous stock in such a manner as to permit formationinto a continuous web by conventional paper machine equipment, withoutgumming the instrumentalities thereof; the subsequent drying of such webby conventional means and theuniting or consolidation under heat andpressure of the web or webs thereby formed to produce a homogeneous andrigid structure. Accordingly, it is an object of the invention toprovide an improved process wherein the fibre and resin are caused tointermix and combine readily and to obtain and retain their homogeneousadmixture in the final article.

In accordance with the invention, the resin is combined with any desiredor conventional fibrous stock or pulp in a beater or some equivalentdevice in such a manner as to distribute the resin throughout the massof pulp. he admixture, having been brought to the proper pulpconsistency, is then passed over a conventional board forming or paperforming machine to deposit the solid constituents and remove the water,and the resulting product, after drying, is consolidated under heat andpressure.

Extracted pine wood pitch constituting the resin employed in accordancewith our invention is a complex resinous material whose exactcomposition is unknown, and comprises the residue, solid'at normaltemperatures, left after the separation of rosin, turpentine and othervaluable constituents oipine wood. It has heretofore been consideredsubstantially commercially valueless and has ordinarily been discarded.l

The extracted pine wood pitch comprises a. residue low in abietic acidremaining after the separation of refined rosin high in abietic acid'uble matter, depending upon from the resinous material obtained byextraction of pine wood with a solvent. It is characterized bysubstantial insolubility in cold petroleum hydrocarbons, but will differsomewhat in its specific characteristics, such as acid number, meltingpoint, extract petroleum ether solubility and content of naphthaandtoluol-solthe method for the recovery of rosin from pine wood used initsproduction.

As is well known, rOsin may be extracted from pine wood by the use of asuitable solvent, such as hot gasoline, benzol, et cetera, after steaminof the wood with live steam to remove volatile oils, such as turpentineand pine oil. Again, volatile oils, as turpentine, and pine oil, may beextracted'with the resin without first steaming for their removal.

Following extraction, the extract is distilled for the removal ofsolvent in those cases where the wood was subjected to steaming beforeextraction; or for the removal of solvent and volatile oils, asturpentine and pine oil, in those cases where the wood was extracteddirectly without steaming. As the result of distillationa resinousmaterial containing abietic acid and admixed impurities is obtained.This resinous material may be treated in any one of a number of ways,all known to the art, for the removal of refined rosin high in abieticacid. The residue remaining after the removal of refined rosin andcomprising a dark colored, hard, resinous mass low in abietic acidconstitute the extracted pine wood pitch employed in our invention. Acommercial variety of. such a resin is known by the trade name ofVinsoP. The resin is soluble in alcohol and has a melting point ofapproximately 225-235" F., ball and ring method, and a penetration ofzero at 160 F., five at 180 F., and seventy at 210 F., (200 grams, 5seconds). It is peculiarly characterized by absence of cold fiow to theextent that, when powdered, the particles show substantially no tendencyto cohere, even under summer heat or when subjected to considerablepressure. These properties are associated with extreme inertness totemperature changes as may be determined by penetration-temperaturetests made in accordance with conventional methods, as reflected by thepenetration-temperature tests above referred to. These propertiesdistinguish this resin from the well known pitches and bituminousmaterials of which we have knowledge. It is preferred to use a resinhaving a penetration of less than fifteen hundredths of a centimeter at180 F.

By virtue of these properties, the resin becomes peculiarly adapted tothe fulfillment of the objectives contemplated by this invention. It canbe powdered, stored in bags and shipped during hot weather withoutsintering together of the particles. Likewise, the absence of cold flowand the ability to resist press roll pressures on a paper machinewithout developing adhesiveness renders it capable of use on a paper orboard machine without the presence of protective materials which areordinarily necessary to prevent gumming of the instrumentalitiesthereof. These properties carry through into the finished product andimpart to the finished product the structural stability and resistanceto deformation heretofore noted. I

We have found that the resin employed in accordance with our inventioncan be directly compounded or admixed in powdered form with the pulp inthe beater. As an aid thereto, use may be. made of so-called wettingagents, such as any of the well known higher fatty acid sulfonates andtheir sodium salts, Turkey red oil, various soaps, and alkyl arylsulfonates. Among other soi-called wetting agents which may be employedare the sodium salts of naphthalene sulfonic acid derivatives sold underthe name of Alkanol B, as well as the free naphthalene sulfonic acidknown as Neomerpin. By the term wetting agent." as employed in thepresent specification and claims, it will be understood that referenceis had to all agents of this class which are capable of permitting rapidintermixing of the resin with the aqueous contents of the beater, whileretaining the resin in such form as to permit it to attach itself aboutthe fibers. When use is made of a wetting agent, the charge isintroduced into the pulp in the beater by first kneading or mixing theresin together with the wetting agent and a small amount of water toform a uniform slurry, which may be piped or otherwise carried into thebeater.

In accordance with the invention, the fibrous pulp or paper stock may beof any conventional type, comprising vegetable fibers capable of beingformed into sheets or layers, such as rag, sulphite or kraft pulps, orthe pulps formed from waste papers, it being understood by anyoneskilled in the art that the characteristics of the final product willdepend in some degree upon the stock employed. The invention in itsbroadest aspect, however, contemplates the use of pulps of the typeemployed in making such materials as so-called asbestos paper or boardand the like. The fibers of this broad class comprise asbestos, mineralwool and even glass fibers. In short, it may be stated that as usedbroadly the terms paper pulp" or fibrous pulp or stock are intended tocover any fibrous material capable of being formed into sheets orlayers, particularly where the fibers are matted or felted. The stockmay be defibered in any conventional beater, such as the well-knownHollander beater, preferably in the conventional aqueous medium.

Our invention contemplates the addition of a substantial proportion ofthe resin. Products having good structural properties have been formedfrom pulp mixtures containing a quantity of resin substantially equal inweight to, the weight of the admixed fibers, as well as from mixturescontaining from forty to sixty percent, of the resin with respect to thetotal resin fiber mixture. On the other hand, results satisfactory forcertain purposes have been obtained employing from 10% to 70% of resinby weight of the resin-fiber mixture.

The hydrogen ion concentration of the beater stock should be adjusted,preferably by the use of alum, to a condition favorable to the maxi mumretention of the resin upon the fibers.

The aqueous charge of the heater is next run onto any suitable paper orboard forming machinery to form paper or board. The deposition of thesolids occurs in accordance with conventional practice.

Subsequent to formation, the sheet or board strength in the wetcondition so that they. may be freely handled during the drying steps.Dryins may take place at. conventional paper or proximately 100" F. surethen released and the board removed from thejpress; The product is ahard, tough, den'se board drying temperatures since no detrimentaleflect upon the resinous material is caused at such temperatures becausethe resin is thermoplastic, in contrast with many of the known syntheticresins which tend to cure or react at the desirable drying temperaturesso that drying must necessarily be carried out at low temperatures andover long periods of time.

After drying, the board or sheet product is consolidated under heat andpressure conditions correlated to bring about the desired degree ofconsolidation and flow of the resin to produce the homogeneity desired.-We believe that, as a result of such consolidation, the fibers per seare, compressed to such an extent that their natural tendency to absorbmoisture is reduced and it appears that such fibers are locked oranchored in such compressed condition as a result of the solidificationof the fused resin on cooling. The consolidated product retains itsdensity without unmolding at moderately elevatedtemperatures.

To effect the consolidation, the sheet or board may be pressed in a moldor between fiat platens for example under a pressure of from about 100to about 2,000 pounds or more per square inch at a temperature at whichthe desired plasticization 'of the resin occurs. It will be apparentthat the applied pressure and temperature may be varied withinconsiderable limits depending upon the result desired.

Following are illustrative examples of the formation of resinous-fibrousproducts in accord-. ance with our invention. A beater furnish of thefollowing composition is prepared:

Pounds Kraft pulp 40 Resin (e. g..Vinsol) 50 The beater is charged in aconventional manner with the pulp and water, the consistency of theaqueous pulp suspension being adjusted to about 4%. After defiberizationof the pulp, the resin is added in the form of a finely divided powderand thoroughly admixed with the stock in the beater. Sufiicient alum isadded to adjust the beater stock to a condition favorable to a whichordinarily do not exceed 180 F. The dried Qboardrnay be'rolled orcalendered prior to consolidation although the rolling or calenderingstep ir ay be omitted. The sheet is now ready forconsolidation and afterbeing dusted with an i-stick preparation, such as zinc stearate orcalcium.stearatejissubjected to compacting between fiat platens at atemperature of approxiximately 825 pounds per square inch, for a riodofapproximately five minutes. The ternperatu e is then rapidly reduced,by passing a cooling medium through the press platens, toaporslightlylower. The pres-,

materialhaving excellent structural properties p eind' havingf notendency to separate; The sheet "prior topressing is preferablyconditioned to 'a moisture content of approximately 44%;

mately' 220-250. F. and under a pressure of appaper or board for suchuses as a may be an alkyl aryl sulphonate such as Nacconol NR (56 grams)are made up into a thin slurry with sufiicient water (48 pounds)to-thoroughly wet out the powdered resin. ,In this procedure the thinslurry of the powdered resin and wetting agent are added to the stock inthe beater in the same manner as the powdered resin itself was added inthe example.

Where it is desired to produce a black product, a black pigment may beused such as any of the conventional carbon blacks. When a carbon blackpigment is used, the carbon black (about 2 pounds) may be advantageouslyincorporated in the aqueous slurry of the wetting agent and the powderedresin, or when a wetting agent is not used, the carbon black andpowdered resin may be incorporated directly into the fibrous stock inthe-beater.

Instead of sheeting the stock on a wet machine, it may be formed on acylinder board machine having one or more cylinders. Like the productmade by consolidating a single thick layer made on a wet machine, theproduct of the multicylinder board machine after consolidation underheat and pressure is a homogeneous unitary product having no tendency toseparate. The sheet or board may likewise be formed on a Fourdriniermachine, as well as on any of the machines commercially used in theformation of insulating board, wall board, and the like.

As a feature of this invention, a plurality of dried sheets may becomposited under heat and pressure to produce a homogeneous unitaryproduct. Thus, in the fabrication of angular and curvilinear productsfrom the sheets or boards made in accordance with our invention aplurality of plies of our product may be composited under heat andpressure and the resulting product has an integral homogeneous structureresistant to delamination of the plies.

Our consolidated product has the distinctive property of reproducing thesurface of the pressing means and permanently retaining at normaltemperature the surface imparted thereto by the pressing means. We referto this as surface stability, i. e. the surface will not be damaged oncontact at normal temperatures with warm moist objects such as thefingers, as distinguished from thermo-plastic-fibrous compositions madewith bitumen-pitch type materials, cumar resin and the like. The surfaceis non-sticky and is glossy when the surface of the pressing means ispolished. I The product is reasonably resistant to relatively dilutemineral and organic acids, and is extremely tough and stiff.

In view of the rapidity with which the sheets or boards may be pressedor consolidated various ent product lends itself to rapid economicalproduction while many hitherto known resins necessitate excessively longcuring or reacting steps,

. thus tying up'expensive pressing equipment.

In accordance with the invention the entire process; including dryingand consolidating, may

be carried out continuously. As is pointed out above, the board may becontinuously dried as rapidly as desired by any conventional means andmay emerge from the drying step at just the temperature for properpressing. From this point the preheated material may be delivereddirectly to the pressing equipment and compacted quickly. Proceeding inaccordance with this process, the pressing means may or may not beheated.

Satisfactory results have been obtained when employing pressing meanswhich were unheated, the residual heat from the pro-heating operationbeing sufllcient to permit the desired compacting of the mass in thepress. For better results, however, it is preferred that the pressingmeans be heated somewhat to prevent too rapid chilling, butnevertheless, to a temperature below the proper consolidatingtemperature so that the product may be removed from the pressing meansThus, the pressing time may vary within a range.

of the order of seconds to 10 or more minutes, depending on thethickness of the board or sheet; the extent to which the sheet or boardis preheated, if at all, and other factors.

We have found that it is desirable to have a certain amount of moisturein the sheets or boards being pressed during the pressing opera-- tion,one of the advantages being that it permits the use of lowertemperatures to obtain the homogeneous product desired. Particularlywhere a plurality of sheets are to be consolidated, the moisture contentof the sheets must be carefully controlled. Moisture in excess ofapproximately 7%- appears to cause sticking of the fibrous structur'e tothe surfaces of the pressing means or blistering, or both. Belowapproximately 4% moisture, it appears that materially highertemperatures are required during pressing.

While we have described our invention in connection with the productionof sheets. or boards, it is to be noted that the invention in its broadaspects is applicable to the production of any felted fibrous structureutilizing the resin of our invention, including felted fibrous productsformed by the accretion of the fibre-resin mixture. on foraminated formsof irregular contour.

It will be apparent that the optimum temperature and pressure forsatisfactory consolidation to produce the desired homogeneous finalprodact will vary depending on a number of factors.

The temperature and pressure of course must be so correlated as to bringabout the desired amount of consolidation at the most efilcienttemperature and pressure. Depending on the pressure, it may be stated asa general rule that consolidation should take place at a maximumtemperature beyond which so much resin would amas be extruded or pressedfrom the sheet that the product would be deficient in its properties. Itis an advantage of the invention that lower proportions of the resinmay, within certain limits, bemade interchangeable with higherproportions thereof, by increasing to a sufficient degree thetemperatures and pressures employed in the step of consolidating thedried sheet, so as to insure a complete fusion of the resin particlesuniformly throughout the sheet. Thus the required densification may beobtained within a relatively wide range of resin content. so that theproduction of satisfactory board is not dependent upon too exacting acontrol of the amount of the resin employed.

Whilethe preferred'embodiment of our invention comprises the use of heatand pressure during consolidation to produce the desired homogeneousfinal product, it is to be understood that for certain purposes, theintermediate product containing the particles of resin distributedthroughout the mass of felted fibers may be sub- Jected to temperaturealone sufiiciently high to cause the resin particles to fuse andcoalesce with each other to form films surrounding the fibers.

By the use of the expression substantiallychemically unaltered incertain of the claims, we intend to distinguish the properties of theresin when employed as herein described from the properties resultingwhen it is employed as a size, 1. e., in the form of an alkali soap ofthe resin, from which an insoluble soap of the resin is precipitated bychemical reaction with alum or the like, as described, for example, inpatent to Dreshfield 2,168,399, dated August 8, 1939. y

We claim as our invention:

1. The process of producing consolidated sheet material which comprisesproviding a fibrous stock of pulp fibres in. uniform mixture with asubstantial proportion of a powdered thermoplastic resin, said resinconsisting essentially of a residue low in abietic acid remaining afterseparation of refined rosin high in abietic acid from the resinousmaterial obtained by extraction of pine wood with a solvent, subjectingthe mixture to a sheet forming operation, adjusting the moisture contentof the sheet to from about 4 to about 7%, consolidating the resultingproduct by heating it to a temperature of from about 220 to about 250F., to plasticize the resin and subjecting it to a pressure of fromabout to about 2,000

pounds per square inch to cause the plasticized resin to now andpermeatetne fibrous structure and to substantially completely surroundthe individual fibres thereof and substantially an the intersticesbetween them, cooling the sheet to solidify the resin in blended stateand to anchor the fibres in compressed condition, releasing thepressure, and recovering the cooled product as a hard, stiff, toughsheet material having the property of remaining consolidated andrigidified and of retaining its density without unmolding.

2. In a process of producing a hard, dense board-like homogeneousfibrousstructure wherein a mixture of pulp fibres and a substantial proportionof a powdered thermoplastic resin is sheeted, said resin consistingessentially of a substantially chemically unaltered residue low inabietic acid remaining after the separation of refined rosin high inabietic acid from the rosinous material obtained by the extraction ofpine wood with a solvent, the improvement which comprises conditioningthe sheet material to a spams: v 5

moisture content of approximately 4 to 6%. con--* solidating a pluralityof such sheets at a temperature of from about 220 to about 250 l"., anda pressure of from about 100 to about 2,000 pounds per square inch for aperiod 01' from about 10 seconds to about 10 minutes to cause the resinto flow and to substantially uniformly permeate the fibrous structure,cooling the consolidated product to solidify the resin in blended state.and to anchor the fibres in compressed condition, releasing the pressureand recovering the cooled product as a homogeneous hard, dense,board-like product substantially free of tendency to delaminate atnormal temperatures.

W. RICHTER. HAROLD R. GILLEI'I'E.

